1. Field of the Invention
The present invention relates generally to linkage apparatus provided on cross country skis for the attachment of ski boots to the skis. More particularly, the present invention is directed to an improvement of linkage apparatus in which the linkage element is an elongate elastic element in the shape of a blade positioned to interconnect the ski and the boot which is provided with a pre-stressed moment when attached to the ski which counteracts the tendency of the elastic elongate element to lift off the ski in the absence of externally applied force.
2. Description of Background and Material Information
French Patent No. 2,447,731, commonly owned with the present application, describes a linkage apparatus in which the ski, or other support element, is provided with an upper horizontal surface adapted to receive an elastic blade, known as a flexion blade, which forms a connection between the ski and the tip of the boot. The anterior section of the flexion blade is fitted in a housing attached to the upper surface of the ski in a manner so as to be pressed against the upper surface of the support element. The posterior section of the flexion blade is free or otherwise unattached to the upper surface of the ski. The rear end of the flexion blade is adapted to receive, in a removable fashion, the front end of a boot or shoe by means of an appropriate boot insertion mechanism. Typical boot insertion mechanisms include an attachment ring, a pivotable lever and a support plate. In the course of use, the movements applied by the skier principally involve pivoting the boot with respect to the ski in a longitudinal vertical plane. Such action results with a corresponding flexing of the flexion blade generally around an axis extending transversely through a region of reduced thickness of the flexion blade in which the flexing preferably occurs. After a certain amount of use, however, it appears that the flexion blade exhibits a permanent deformation in its pivot or flexing zone of reduced thickness, due to the fatigue of the material from which it is formed, such that the posterior region of the blade, when the blade is at rest, rises away from the upper surface of the ski in a substantially lifted-off position.
This phenomenon is disadvantageous in that a space results between the flexion blade and the upper surface of the ski. This gap allows snow to become lodged between the upper surface of the ski and the lower surface of the flexion blade in this important region of the binding. The presence of snow or ice in this region of the binding can prevent the blade, and consequently the boot, from flattening against the ski to the discomfort and inconvenience of the skier during skiing.
Another disadvantage which stems from the deformation of the blade is more of a psychological concern than a practical problem. When a skier observes the permanent deformation of the flexion blade, as discussed above, the skier tends to associate the deformation of the blade with a deterioration of the linkage apparatus. Although the disadvantages relating to snow pose real problems from the standpoint of performance, the deformation of the blade does not adversely affect the durability of the binding apparatus nor is it indicative of deterioration of the flexion blade.
It has been observed that the previously discussed disadvantages occur with linkage apparatus in which the toe of the boot is fixed in a removable fashion at the posterior end of the flexion blade, as well as with linkage apparatus in which the flexion blade is integral with the toe area of the boot. In this latter case, however, the permanent deformation by fatigue of the flexion blade is less perceptible and problems caused by snow becoming packed between the blade and the upper surface of the support element while the boot and its integral flexion blade are disengaged from the ski do not occur.